Probably because it's a roll of the dice due to the multiple variable that go into flow. If things stay the same and each flows their numbers with no changes, my guess would be that PDT with flow a today hire the quickest. ENY is flowing the most today with the largest pilot group but that is set to reduce. My guess would be that AAL plans to level the playing field and have all three with approximately the same flow time... but who knows. Too many variables, a flow is a great backup plan while you attempt to get hired somewhere -- but again that's just my opinion.

Hope that helps.